Differential amplifiers and current steering circuits are known in the art. Typically, differential amplifiers and current steering circuits are realized by employing semiconductor active devices such as, for example, field effect transistors. Field effect transistors, being semiconductor based and providing for charge transport in a condensed matter medium suffer from an inherent limitation in the maximum transport velocity which can be attained. This transport velocity limitation is typical of all bulk transport devices. Further, semiconductor based active devices function in a manner which requires that during switching periods excess charge carriers must be removed from areas within the device. In the instance of bi-polar transistor devices stored charge must be removed from the base region. In the instance of field effect transistors charge must be re-distributed in the region of the device channel. The velocity limitation and charge re-distribution effects required result in an upper frequency limitation above which semiconductor devices may not be practically employed.
Many systems applications may be anticipated wherein data transmission rates and/or operating frequencies are desired which can not be conveniently achieved by employing known semiconductor switching devices.
Accordingly there exists a need for an active device which overcomes at least some of the shortcomings of the existing art.